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Merino Martinez, R. (author), VanDercreek, Colin (author), Snellen, M. (author)Aeroacoustic measurements with microphones in closed-section wind tunnels are typically hampered by the pressure fluctuations of the turbulent boundary layer (TBL) on the tunnel's walls, ceiling, or floor, where phased microphone arrays are usually mounted. This paper evaluates the performance of several advanced acoustic imaging methods that...conference paper 2022
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Merino Martinez, R. (author), von den Hoff, B. (author), Morata, David (author), Snellen, M. (author)Complex test models in aeroacoustic experiments often present an arrangement of noise sources within a three–dimensional space. Planar microphone array normally have difficulties in separating sound sources in the direction normal to the array plane due to their poorer spatial resolution in this direction. This paper evaluates the benefits of...conference paper 2022
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von den Hoff, B. (author), Merino Martinez, R. (author), Simons, D.G. (author), Snellen, M. (author)Complex acoustic systems typically present three-dimensional distributions of noise sources. Conventional acoustic imaging methods with planar microphone arrays are unsuitable for three-dimensional acoustic imaging, given the computational demands and the incapability to explicitly account for the presence of multiple sources. This paper...journal article 2022
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Lima Pereira, L.T. (author), Merino Martinez, R. (author), Ragni, D. (author), Gómez-Ariza, David (author), Snellen, M. (author)This paper explores the advantages of combining asynchronous microphone array measurements for acoustic source mapping in two and three–dimensional applications. Four different approaches are considered, three consisting of the combination of the source maps (arithmetic mean, geometric mean, and minimum value), and a fourth one obtained by...journal article 2021
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VanDercreek, Colin (author), Merino Martinez, R. (author), Sijtsma, P. (author), Snellen, M. (author)Aeroacoustic measurements performed by flush-mounted microphone arrays on the walls of closed-section wind tunnels are contaminated by the hydrodynamic pressure fluctuations of the wall's boundary layer. This study evaluates three different microphone cavity geometries for mitigating this issue. Their improvement to the signal-to-noise ratio ...journal article 2021
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Merino Martinez, R. (author), Luesutthiviboon, S. (author), Zamponi, R. (author), Rubio Carpio, A. (author), Ragni, D. (author), Sijtsma, P. (author), Snellen, M. (author), Schram, Christophe (author)In this paper, the performance of four acoustic imaging methods: conventional frequency domain beamforming (CFDBF), functional beamforming (FUNBF), enhanced high resolution CLEAN–SC (EHR–CLEAN–SC) and generalized inverse beamforming (GIBF), is investigated in terms of accuracy and variability. Three experimental test cases are considered: 1)...journal article 2020
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VanDercreek, Colin (author), Merino Martinez, R. (author), Snellen, M. (author), Ragni, D. (author), Simons, D.G. (author)This paper analyses the influence of microphone cavity geometry on beamforming measurements with a turbulent boundary layer present on the microphone array. A 16- microphone array was tested in the anechoic open-jet wind tunnel of the Delft University of Technology. The array was placed on a flat plate mounted flush with the exit nozzle of the...conference paper 2020
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Merino Martinez, R. (author), Herold, Gert (author), Snellen, M. (author), Dougherty, Robert P. (author)Functional Projection Beamforming (FPB) is a method proposed by Dougherty in 2019, based on functional beamforming. It yields the integrated sound spectrum for a given region of integration (ROI) within the functional beamforming source map. FPB does not suffer from the loss of level that can affect functional beamforming, especially for coarse...conference paper 2020
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Merino Martinez, R. (author), Neri, Eleonora (author), Snellen, M. (author), Kennedy, John (author), Simons, D.G. (author), Bennett, Gareth J. (author)The noise emissions of a full-scale nose landing gear (NLG), measured in a wind tunnel and obtained from computational simulations, are compared with those of three regional aircraft types recorded in flyover measurements. A comparison is made with the noise prediction models of Fink, Guo, and German Aerospace Center (DLR). A good agreement...journal article 2020
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Merino Martinez, R. (author), Snellen, M. (author)Landing gear noise is considered the dominant airframe noise source on aircraft during approach. Previous studies indicated the presence of a strong tonal sound on flyovers of several commercial aircraft types, and suggested that it was caused by the interaction of open cavities in the nose landing gear (NLG) system with the flow. Airframe...conference paper 2020
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Vieira, A.E. (author), Snellen, M. (author), Malgoezar, A.M.N. (author), Merino Martinez, R. (author), Simons, D.G. (author)Engine noise shielding is an important measure towards low-noise aircraft configurations. Such designs are supported by prediction tools that indicate high values for shielding of engine noise. Most prediction models approximate the complex nature of engine noise to simple noise sources such as monopoles or dipoles. This work compares...journal article 2019
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Merino Martinez, R. (author), Sijtsma, P. (author), Snellen, M. (author), Finez, A. (author), Herold, G. (author), Malgoezar, A.M.N. (author), Pereira, A. (author), Sarradj, E. (author), Simons, D.G. (author)Phased microphone arrays have become a well-established tool for performing aeroacoustic measurements in wind tunnels (both open-jet and closed-section), flying aircraft, and engine test beds. This paper provides a review of the most well-known and state-of-the-art acoustic imaging methods and recommendations on when to use them. Several...journal article 2019
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Rubio Carpio, A. (author), Merino Martinez, R. (author), Avallone, F. (author), Ragni, D. (author), Snellen, M. (author), van der Zwaag, S. (author)The hydrodynamic and acoustic fields for a NACA 0018 with solid and porous trailing edge inserts are investigated. The porous inserts, covering 20% of the chord, are manufactured with metal foams with cell diameters of 450 and 800 μm and permeability values of 6 × 10−10 and 2.7 × 10−9 m2. The experiments are performed at a chord-based Reynolds...journal article 2019
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Merino Martinez, R. (author), Pieren, R.D. (author), Snellen, M. (author), Simons, D.G. (author)Noise emissions from wind turbines are one of the main issues that the wind energy industry must deal with nowadays. Strict noise regulations often prevent wind turbines to operate at maximum power conditions, causing large losses of power production and, hence, of revenue. Several noise reduction measures have been proposed so far, but the...conference paper 2019
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Luesutthiviboon, S. (author), Malgoezar, A.M.N. (author), Merino Martinez, R. (author), Snellen, M. (author), Sijtsma, P. (author), Simons, D.G. (author)The recently introduced high-resolution (HR)-CLEAN-SC algorithm for acoustic imaging provides ‘super-resolution’, i.e. the ability to discern sound sources located closer than the Rayleigh resolution limit. This is achieved by allowing the source markers to be relocated from the actual source locations within a certain constraint to avoid the...journal article 2019
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Merino Martinez, R. (author), Vieira, A.E. (author), Snellen, M. (author), Simons, D.G. (author)Aircraft noise is an increasingly important issue that causes annoyance and complaints for the communities living in the vicinity of airports. The conventional sound metrics (such as the A–weighted sound pressure level) typically used for assessing the impact of aircraft noise often fail to conveniently represent the actual annoyance...conference paper 2019
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Merino Martinez, R. (author), Sijtsma, P. (author), Rubio Carpio, A. (author), Zamponi, R. (author), Luesutthiviboon, S. (author), Malgoezar, A.M.N. (author), Snellen, M. (author), Schram, Christophe (author), Simons, D.G. (author)Most acoustic imaging methods assume the presence of point sound sources and, hence, may fail to correctly estimate the sound emissions of distributed sound sources, such as trailing-edge noise. In this contribution, three integration techniques are suggested to overcome this issue based on models considering a single point source, a line...journal article 2019
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Vieira, A.E. (author), Mehmood, Umair (author), Merino Martinez, R. (author), Snellen, M. (author), Simons, D.G. (author)The capacity of airports is limited due to the negative community response to noise. Traditional metrics, such as the A-weighted maximum sound pressure level (Lp;A;max), indicate the overall noise generated by an aircraft flyover but do not provide any information on tonal components or frequency variations in time that are known to affect...conference paper 2019
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Merino Martinez, R. (author), Sijtsma, P. (author), Snellen, M. (author)Most acoustic imaging methods assume the presence of point sound sources and, hence, fail to correctly estimate the sound emissions of distributed sound sources (such as trailing– edge noise). In this contribution, three integration techniques are suggested to overcome this issue based on models considering a single point source, a line source...conference paper 2018
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Merino Martinez, R. (author), Sanders, Martinus P.J. (author), Caldas, Luciano C. (author), Avallone, F. (author), Ragni, D. (author), de Santana, Leandro D. (author), Snellen, M. (author), Simons, D.G. (author)Microphone arrays are useful measurement devices for estimating the location and strength of sound sources. Numerous comparative studies have been conducted regarding the performance of acoustic imaging methods in the past, but literature lacks of a systematic investigation on the role of the hardware on the measurements. This research...conference paper 2018
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